1. Field of the Invention
This disclosure generally relates to electrical power systems, and more particularly to a controller for controlling operation of electric drives, for example electric drives associated with electric and/or hybrid vehicles.
2. Description of the Related Art
Power conversion systems transform and/or condition power from one or more power sources for supplying power to one or more loads. A power conversion system component commonly referred to as an “inverter” transforms direct current (DC) to alternating current (AC) for use in supplying power to an AC load. A power conversion system component commonly referred to as a “rectifier” transforms AC to DC. A power conversion system component commonly referred to as a “DC/DC converter” steps-up or steps-down DC voltage. In some embodiments, these components may be bi-directionally operable to perform two or more functions. These functions may, in some cases be inverse functions. For example, a switch mode inverter may be operable to invert DC to AC in one direction, while also operable to rectify AC to DC in another direction. An appropriately configured and operated power conversion system may include any one or more of these components to perform any one or more of these functions.
In common usage, the term “converter” applies generically to all power conversion components whether inverters, rectifiers and/or DC/DC converters and is used herein and in the claims in that generic sense. Power converters typically employ power semiconductor devices, such as insulated gate bipolar transistors (IGBTs), metal oxide semiconductor field effect transistors (MOSFETs), and/or semiconductor diodes. One or more power conversion system components may be provided as a self-contained unit, commonly referred to as a power module, which comprises an electrically insulative housing that houses at least a portion of the power conversion system component, and appropriate connectors such as phase terminals or bus bars.
Many applications employ the delivery of high power, high current and/or high voltage from a power source to a load. For example, it may be desirable in transportation applications to provide a relatively high DC voltage to an inverter to supply AC power for driving a load such as a traction motor for propelling an electric or hybrid electric vehicle. It may also be desirable at the same time to provide relatively low voltage AC or DC power for driving accessory or peripheral loads. Such applications may employ one or more of a variety of power sources. Applications may, for example, employ energy producing power sources such as internal combustion engines or arrays of fuel cells and/or photovoltaic cells. Applications may additionally, or alternatively, employ power sources such as energy storage devices, for example, arrays of battery cells, super- or ultra-capacitors, and/or flywheels. Often, such applications employ a power converter to transform and/or condition the power, for example, stepping down the voltage at which the power is supplied to the load.
Operation of electric drives, particular those employing permanent magnet motors must address a number of issues not presented by other types of drives, such as drives employing internal combustion engines. Additionally, it may be desirable to provide some limited ability to continue operating an electric drive after a fault has occurred. Such capability may be referred to as “limp home” capability, which may, for example, allow operation of the electric drive at reduced power for a time sufficient to move a vehicle to a point of safety. Addressing such problems may be commercially beneficial to the acceptance of electric and/or hybrid vehicles. Thus, new approaches to accurately detect, handle and/or remedy fault conditions in electric drives are desirable.